Work machine such as mining shovels and the like are used for excavation work. Much effort has been aimed at automating the work cycle or portions of the work cycle of such machines.
One such system is disclosed in U.S. Pat. No. 5,404,661 issued to William C. Sahm et al on Apr. 11, 1995. The Sahm system, aimed at a mining shovel, determines the position of a bucket of a work implement as it excavates, i.e., modifies the work site. The position of the bucket as it modifies the work site is used to update a site model or database. The current site model is compared with a desired site model by a differencing algorithm. The output of the differencing algorithm is used to control operation of the work machine or is displayed to the operator to assist in operation.
The work site covers a generally large area. Thus, the database is typically large as well, requiring a resultant large amount of storage space.
There are three general approaches for the structure of the site model. In the first approach, the entire work site is divided into a grid. Each square of the grid represents a fixed point (with fixed X and Y coordinates) in the work site. Data associated with the site is stored at each square. The problem with this approach is that the grid must cover the entire site. Generally, there will be large portions of the site which will not be affected or worked on by the work machine. Thus, large amounts of storage space may be wasted.
In the second approach, only those points required are stored. However, since the grid structure is not used, each of these points requires that the X and Y coordinates of the point be stored as well. This also wastes storage space.
In the third approach, a Triangular Irregular Network, or TIN, is used. The TIN is composed of a plurality of points having X and Y coordinates. For each point in the network, the database stores elevation information and, for each point, the other points to which it is connected. The TIN is used to give a better approximation or representation of the work site. One factor which allows the TIN to be more accurate is that the points composing the network are not regular. The positions of the points are dictated by the surface of the work site. As a result, given a point contained within one of the triangles of the network, it becomes more difficult to determine which triangle includes the point and thus harder to determine its elevation.
The present invention is directed at overcoming one or more of the problems as set forth above.